1. Field of the Invention
The present invention concerns an apparatus for simultaneously monitoring reactions taking place in a plurality of reaction vessels comprising a metallic vessel holder with a plurality of chambers, the side wall of each of these chambers being formed to smoothly hold in an upright position a removable and transparent reaction vessel.
More particularly, the invention concerns an apparatus wherein the monitoring is carried out by measuring fluorescence light emitted by sample-reagent mixtures when they are excited by light provided by a suitable light source, such as a light of short wave-length.
2. Description of the Prior Art
An apparatus for the automatic execution of temperature cycles is known from EP 0 642 831 A1. This apparatus comprises a circular holder for twelve reaction vessels, each of these vessels containing sample-reagent liquid mixtures of about 100 .mu.l. The holder is metallic and allows fast transmission of the different temperatures of the cycles from a controlled Peltier element to the mixtures.
A system for real time detection of nucleic acid amplification products is known from WO 95/30139 A1. This system allows fluorescence-based measurements on a plurality of sample-reagent liquid mixtures within small vessels at different, varying temperatures. The excitation light arrives at the vessels from the top side via a fiber optic and a focal lens. The fluorescent light is collected via the same way in opposite direction and is transmitted to a centralized optical separation and analyses component.
There are important disadvantages of the described devices. With the circular array of vessels disclosed by EP 0 642 831 A1 only a relatively low number of vessels can be positioned on a single Peltier element. Therefore, only a small part of the area available on a Peltier element for thermal cycling of such vessels is used.
In order to carry out temperature cycles on a high number of reaction vessels arranged in a circle, it would be necessary to use more than one Peltier element for cooling and heating. This is not desirable because Peltier elements are rather expensive. In the apparatus disclosed by WO 95/30139, the excitation light path and the fluorescence light path are close to each other, and this increases the possibility of undesirable interferences.
Therefore, with the structure of the above-mentioned known devices it is not possible to provide a very compact array of reaction vessels which is suitable for performing thermal cycling of a plurality of sample-reagent mixtures contained in reaction vessels positioned on a thermal block.